(a) Field of the Invention
The present invention relates to a hybrid vehicle. More particularly, the present invention relates to an oil pump control apparatus of a hybrid vehicle that controls an oil pump according to a demand for output torque and oil temperature, and a method thereof.
(b) Description of the Related Art
Demand for an environmentally-friendly vehicle has increased by reinforcement of exhaust gas regulations and enhancement of fuel efficiency concerns, and hybrid vehicles have been spotlighted as a realistic alternative.
A hybrid vehicle can be distinguished from a fuel cell vehicle and an electric vehicle in a narrow sense, and the hybrid vehicle in this specification can include a fuel cell vehicle and an electric vehicle in a broad sense and can designate a vehicle that has an engine and at least one high voltage battery and a motor that is operated by the battery. The engine and a motor are applied to a hybrid vehicle as power sources, and are appropriately combined according to driving conditions to enhance fuel efficiency and to reduce exhaust gas emission.
Hybrid vehicles improve fuel consumption efficiency by combining power from the engine and the motor when the engine and the motor are operated. Hybrid vehicles adopt a hybrid stop and go (HSG) function to automatically turn the engine on or off according to a driving conditions. Additionally, when the hybrid vehicle is in an electric vehicle (EV) mode, the engine may also be turned off to conserve fuel.
As described above, if the engine is turned off, a mechanical oil pump that is connected to a crankshaft of the engine to supply an automatic transmission of the vehicle with oil stops operating. Thus, hydraulic pressure is not properly supplied to the automatic transmission and a wet engine clutch as it should be. Accordingly, normal line pressure is not formed in the automatic transmission so that friction elements (clutches and brakes) realizing a forward first speed are released.
Typically, an electric oil pump is disposed in parallel with the mechanical oil pump to resolve the above problem in hybrid vehicles. This electric oil pump is configured to be operated independently from the engine and thus is typically able to supply the proper hydraulic pressure to the automatic transmission and the wet engine clutch.
However, when the engine is turned off by the HSG function, the electric oil pump must rotate at a high speed. Thus, the durability of these electric pumps is greatly deteriorated, the current of a battery is excessively spent, and the battery must be more frequently charged and discharged, thus affecting the durability of the battery.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.